A new self-organizing mechanism for deep-focus earthquakes

  title={A new self-organizing mechanism for deep-focus earthquakes},
  author={H. Green and P. Burnley},
THE mechanism of deep-focus earthquakes has been a puzzle since their discovery almost 70 years ago1, 2, because brittle fracture and frictional sliding at depths in excess of 100–200 km would require unrealistic rock strengths3, 4. Rock strength does increase with pressure, but a few hundred MPa (equivalent to 10–20 km depth) suffices to inhibit most fracture, and elevated temperature activates ductile mechanisms that operate at stresses less than the fracture stength. A range of mechanisms… Expand
The failure mechanism for deep-focus earthquakes
Abstract Experimental deformation of Mg2GeO4 olivine at pressures between 1 and 2 GPa in the spinel stability field has led to discovery of a faulting instability that develops at theExpand
Shearing instabilities accompanying high-pressure phase transformations and the mechanics of deep earthquakes
  • H. Green
  • Geology, Medicine
  • Proceedings of the National Academy of Sciences
  • 2007
Extensive seismological interrogation of the region of the Tonga subduction zone in the southwest Pacific Ocean provides evidence suggesting significant metastable olivine, with implication for its presence in other regions of deep seismicity. Expand
Anticrack-associated faulting at very high pressure in natural olivine
SHALLOW earthquakes are produced by brittle shear fracture of rock and/or fictional sliding on pre-existing fault surfaces1. At very high pressures, however, brittle fracture and frictional slidingExpand
Deep-Focus Earthquake Analogs Recorded at High Pressure and Temperature in the Laboratory
Microstructural observations prove that dynamic weakening likely involves superplasticity of the nanocrystalline spinel reaction product at seismic strain rates, and explores the feasibility of phase transformations of metastable olivine that might trigger deep-focus earthquakes in cold subducting lithosphere. Expand
Fast rise times and the physical mechanism of deep earthquakes
EARTHQUAKES at depths of > 300 km are similar to shallower events in that they are dominantly of double-couple character1, implying that shearing motion has taken place at depth. But becauseExpand
Mechanisms of deep earthquakes
In most tectonic settings, no earthquakes occur below about 30 km depth. This is because increasing pressure inhibits frictional sliding, whilst increasing temperature promotes ductile deformation.Expand
Mechanism of Deep - Focus Earthquakes Inferred from High Pressure Experiments
Deep-focus earthquakes occur at depths from the earth's surface up to 680 km (corresponding to pressure of 24 GPa). They occur only in the restricted areas in the earth, or the subduction zones.Expand
Experimental evidence for wall-rock pulverization during dynamic rupture at ultra-high pressure conditions
Abstract The mechanisms triggering intermediate and deep earthquakes have puzzled geologists for several decades. There is still no consensus concerning whether such earthquakes are triggered byExpand
Chapter 15 - The Anticrack Mechanism of High-Pressure Faulting: Summary of Experimental Observations and Geophysical Implications
This chapter illustrates the anticrack mechanism of high-pressure faulting. It summarizes the experimental observations and geophysical implications. The anticrack faulting hypothesis provided forExpand
Are intermediate depth earthquakes caused by plastic faulting
Abstract The increase in confining pressure and temperature with depth precludes frictional sliding beyond a few tens of kilometers, yet earthquakes occur to depths greater than 600 km. Although rockExpand


Localized polymorphic phase transformations in high‐pressure faults and applications to the physical mechanism of deep earthquakes
Earthquake mechanisms based on frictional instabilities are widely accepted for relatively shallow earthquakes. Such mechanisms, in unmodified form, are highly unlikely for deep earthquakes becauseExpand
Deep‐earthquake initiation by phase transformations
The following mechanism for deep earthquakes is proposed: Due to the relative motion of mantle and plate, material crosses a phase stability line. The new phase, with a different molar volume, isExpand
Earthquakes and faults
Abstract The hypothesis that earthquakes are caused by faulting has been prominent in seismological theory for half a century, but continues to present many difficulties. Although the chief supportExpand
Phase transformations, earthquakes and the descending lithosphere
Abstract The energy dissipated from metastable phase transformations is investigated in this paper. In addition to the kinetic energy envisaged by Randall, at least two other major forms of energyExpand
Olivine‐spinel transitions: Experimental and thermodynamic constraints and implications for the nature of the 400‐km seismic discontinuity
The sequence of high-pressure phase transitions α→β→γ in olivine is traditionally used as a model for seismic velocity variations in the 200- to 650-km-depth interval in a mantle of peridotitic bulkExpand
Plastic instabilities: Implications for the origin of intermediate and deep focus earthquakes
Adiabatic or catastrophic plastic shear has been reported in metals, polymers, and metallic glasses. The phenomenon is associated with rapid stress drops and audible pings or clicks as the materialExpand
Shear instability in a viscoelastic material as the cause of deep focus earthquakes
The mechanism of deep focus earthquakes has been examined by numerical and linear analysis of shear instability in subducting slabs. We assume subducting slabs deform such that the spatially averagedExpand
Stress dependence of the mechanism of the olivine–spinel transformation
OLIVINE, α-(Mg,Fe)2SiO4, is the most abundant phase in the Earth's upper mantle. It transforms to high-density polymorphs (α, with the spinel structure and β, with a modified spinel structure) underExpand
Thermodynamic constraints on phase changes as earthquake source mechanisms in subduction zones
Abstract Application of thermodynamic equations for phase transitions with a shock wave output from metastable to stable phases that are believed to occur in subduction zones indicates that whileExpand
Source wave forms of three earthquakes
Strain seismograms of the Montana shallow earthquake of August 17, 1959 recorded at Isabella, California have the wave pattern predicted in 1904 by Lamb for a surface pressure pulse. This isExpand